• Weight is defined as:

The force acting on an object due to gravitational attraction

• Planets have strong gravitational fields
  • Hence, they attract nearby masses with a strong gravitational force

   

• Because of weight:
  • Objects stay firmly on the ground
  • Objects will always fall to the ground
  • Satellites are kept in orbit

   

Some of the phenomena associated with gravitational attraction and the weight force

• Weight, mass and gravitational field strength are related using the equation:

• This can also be written as:

W = m × g

• g?is known as the acceleration due to gravity or the?gravitational field strength
  • On Earth, this is equal to?9.81?m/s²?(or N/kg)

   

• The weight that an object experiences depends on:
  • The?object's?mass
  • The mass of the?planet?attracting it

   

• Mass?(measured in kilograms,?kg) is related to the?amount of matter in an object
• Weight?(measured in newtons,?N) is the?force of gravity on a mass
  • The weight of an object and the mass of an object are?directly proportional
  • The size of this force depends on the?gravitational field strength?(often called gravity, g, for short)

   

Step 1: State the equation linking weight and mass

• • The equation linking weight and mass is:

   

W = m × g

Step 2: List the known values

• • The question instructs us to take the Earth's gravitational field strength as 10 N/kg
  • The question also instructs us to take the Moon's gravitational field strength as 2 N/kg
  • Mass,?m?= 40 kg

   

Step 3: Calculate Isabelle's weight on Earth

• • Substituting the values of mass and Earth's gravitational field strength into the equation gives:

   

W =?40 × 10 = 400 N

Step 4: Calculate Isabelle's weight on the Moon

• • Substituting the values of mass and the Moon's gravitational field strength into the equation gives:

   

W =?40 × 2 = 80 N

Step 5: Comment on the two values of weight

• • Isabelle's weight is?greater?on Earth than on the Moon
  • This is because the Earth has a?larger?gravitational field strength than the Moon, so Isabelle's weight force (the force of gravity pulling down on her) is larger on Earth than on the Moon